三维有序大孔尖晶石型Li1.6Mn1.6O4的制备及锂离子筛吸附特性

用LiNO3、Mn(Ac)2•4H2O和柠檬酸的混合溶液填充聚甲基丙烯酸甲酯胶体晶体模板, 在空气中氧化焙烧, 制备出三维有序大孔尖晶石型锂锰氧化物Li1.6Mn1.6O4. 前驱体经过0.1 mol/L盐酸脱锂后获得相应的三维有序大孔锂离子筛, 其大孔直径和孔壁厚度分别为240 nm和50 nm左右. XRD测试结果表明, Li1.6Mn1.6O4、锂离子筛和吸锂后的样品均保持尖晶石结构. 三维有序大孔材料呈现彼此连通的孔道空间, 缩短了Li+的平衡吸附时间, 前驱体脱锂率在80 ℃时达到95%, 而锰的溶损率在低于60 ℃时小于2.5%. 溶液温度对Li+的交换能力影响很大, 升高温度, Li+与H+的可逆交换程度增大, Li+的最大吸附容量为56.7 mg/g, 但处于锰16d八面体缺陷位置的氢难于被交换. pH滴定和分配系数(Kd)分析表明, 该固体酸在Li+, Na+和K+共存溶液中对Li+的吸附具有较高的选择性.

Preparation of Three-dimensionally Ordered Macroporous Spinel Li1.6Mn1.6O4 and Adsorption Characteristics of Lithium Ion-sieve

Three-dimensionally ordered macroporous spinel lithium manganese oxide Li1.6Mn1.6O4 was fabricated directly by polymethyl methacrylate colloidal crystal template filled with the LiNO3,  Mn(Ac)2•4H2O and citric acid mixed solution and oxidation roasting in the air atmosphere.  After the precursor was delithiated by 0.1 mol/L hydrochloric acid, three-dimensionally ordered macroporous lithium ion-sieve was obtained,  whose macroporous diameter and pore wall thickness were about 240 and 50 nm,  respectively.  The X-ray diffraction results show that Li1.6Mn1.6O4,  lithium ion-sieve and the lithium-adsorbed samples all keep spinel structure. The three-dimensionally ordered macroporous(3DOM) materials present the channel space connecting each other,  which shortens the adsorption equilibrium time of Li+. The delithiation rate of precursor gets 95% at 80 ℃, while the solution loss rates of manganese are less than 2.5% below 60 ℃.  Solution temperature has great influence on the exchange ability of Li+, raising temperature leads to the increase of Li+ and H+ reversible exchange degree, the Li+ maximum adsorption capacity is 56.7 mg/g, but the hydrogens  in the manganese 16d octahedral defect position are difficult to be exchanged. The analyses of pH titration and distribution coefficient Kd indicate that the solid acid has a high selectivity of Li+ in the coexisting solution of Li+, Na+ and K+.